1. Field of the Invention
The present invention relates to a substrate processing apparatus for performing a series of processes such as thermal processing and chemical liquid processing upon sheet-like substrates (hereinafter referred to simply as “substrates”) such as semiconductor substrates and glass substrates for liquid crystal display, and a substrate transport apparatus to be applied to the substrate processing apparatus.
2. Description of the Background Art
Hithertofore, in a substrate processing apparatus for performing a series of predetermined processes such as thermal processing and chemical liquid processing upon a substrate, a transport robot has been used to transport the substrate between a heating portion for heating the substrate, a cooling portion for cooling the substrate, and a chemical liquid processing portion for processing the substrate using a chemical liquid to perform the series of processes upon the substrate in predetermined order. Such a substrate processing apparatus is typically placed in a clean room in which temperature, humidity and particles are controlled.
In recent years, the diameter of substrate wafers has become greater, and some substrate wafers with a diameter of not less than 300 mm have been handled. The increase in the size of the semiconductor wafers necessitates the increase in the size of processing portions for processing the substrate wafers, accordingly resulting in the increase in the size of the whole substrate processing apparatus.
On the other hand, the increase in the size of the substrate processing apparatus is not desirable in terms of clean room control for the reasons to be described below. The maintenance of the clean room requires special facilities such as a temperature and humidity control unit and a filter, in some cases a chemical absorption filter for resists of a chemical thickening type particularly in recent years. Thus, the increase in the area (referred to hereinafter as a “footprint”) occupied two-dimensionally by the substrate processing apparatus leads to the increase in environmental maintenance costs.
To suppress the increase in the footprint of the substrate processing apparatus, there has been proposed and in use a substrate processing apparatus including processing portions such as the chemical liquid processing portion, the heating portion, and the cooling portion which are vertically stacked in plural tiers.
The substrate processing apparatus with the processing portions vertically stacked in multiple tiers may suppress the increase in the footprint thereof but is disadvantageous in that the height thereof increases as the number of tiers increases. With the increase in the height of the substrate processing apparatus, the height of a transport robot for transporting a substrate to the processing portions also increases.
For transportation of such a fabricated substrate processing apparatus to a semiconductor manufacturing plant, it is necessary to divide the substrate processing apparatus into upper and lower parts because of a freight height limit of transportation means (for example, an upper limit of 2200 mm in the case of air transportation). In this case, it is also necessary to divide the transport robot into upper and lower parts or to remove the transport robot from the substrate processing apparatus for transportation. In either case, the transport robot is required to be reassembled and adjusted in the plant to which the transport robot is transported. This results in the inevitable increase in the number of man-hours needed for transportation and delivery of the substrate processing apparatus.
A solution to be contemplated to such a problem is the use of an extensible mechanism, such as a pantograph structure, as a vertical movement mechanism of the transport robot, with the height of the transport robot in its retracted position being within the freight height limit. This allows the transportation of the substrate processing apparatus, with the transport robot attached to one of the upper and lower parts of the substrate processing apparatus after the division, to eliminate the need to reassemble and adjust the transport robot.
However, the pantograph structure comprises a plurality of pantograph links, and it is impossible to move the transport robot to a level lower than the level or height corresponding to the thickness of the plurality of pantograph links even when the pantograph structure is in its fully retracted position. In some cases, the transport robot is not capable of accessing a processing portion located in a lower tier. To prevent this, the pantograph links should have a greater length so that a smaller number of pantograph links constitute the vertical movement mechanism. This, however, presents a need to consider the space required for the transport robot in its retracted position to ensure an area wherein the transport robot is to be located, resulting in the increase in the footprint of the substrate processing apparatus.